Polymers of diallyldialkyl ammonium compounds have a wide variety of uses. The cationic polymers, for example, can be used as flocculants in water and sewage treatment systems, etc. It has been shown that the higher the molecular weight of the resulting cationic polymer, the more effective the polymer is as a flocculating agent.
Methods for polymerizing diallyldialkyl ammonium compounds are well known in the prior art. See, e.g., U.S. Pat. Nos. 2,926,161; 2,982,749; 3,288,770; 3,461,163 and 4,092,467. Typically, polymerization is effected in an aqueous reaction medium containing a free radical initiator.
Fluoride salts have been reported to accelerate the rate of polymerization and to increase the molecular weight of the formed polymers. Halide salts other than fluoride (e.g., NaCl) did not accelerate polymerization. U.S. Pat. No. 4,742,134.
Where NaCl was formed as a by-product of diallyldialkyl ammonium compound preparation, that salt was reported not to interfere with the polymerization. U.S. Pat. No. 4,151,202.
Those prior studies on the effects of salts on diallyldialkyl ammonium compound polymerization were performed using diallyldimethyl ammonium chloride as the monomer and ammonium persulfate as the free radical initiator. It is well known that persulfate can react with (oxidize) the chloride ion of diallyldimethyl ammonium chloride or NaCl to produce a chlorine radical that serves to terminate polymerization and decrease the molecular weight of the formed polymer. Jaegar et al., J. Macromol. Sci-Chem., A21(5):593 (1984).
It is also known that azo initiators such as 2,2'-azobis(2-amidinopropane) dihydrochloride (V-50) can be used in the polymerization of diallyldialkyl ammonium compounds. By way of example, Japanese Patent No. 56-18611 teaches a method of producing a diallyldimethyl ammonium chloride polymer using water soluble azo-based initiators at temperatures below 55.degree. C. The effects of salts on that polymerization method were not reported.
Azo initiators are further reported to increase the molecular weight of formed polymers where the rate of polymerization is low. The effects of salts on that method were not reported. Jaeger et al., J. Macromol. Sci.-Chem., A21(5):593 (1984).
East German Pat. No. 141, 029 [Chem. Abs., 94, 1222734c (1981) discloses polymerizing diallyldialkyl ammonium compounds in the presence of persulfate initiators and chloride salts but does not disclose that the presence of those ions enhances the rate of polymerization relative to termination or increases the molecular weight of the formed polymer. Because of the oxidation of chloride by persulfate and the chain terminating effects of formed chlorine radicals, this method is not likely to have the effect of increasing the molecular weight of the formed polymer.